<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>example</title>
    </head>
    <body>
        <div id="root" onclick="send(this)">
            <font>aaa</font><img src='http://www.baidu.com'>
        </div>

        <script>
            function send(el) {
                el.getElementsByTagName('img')[0].src = 'http://'
            }
        </script>
    </body>
</html>